ETFs Extend Their Reach, With Unknown Consequences

Buying a government-bond fund is like paying to hear Yo-Yo Ma on the radio. So asserted Peter Lynch back in the 1980s, when he was riding high as manager of the Fidelity Magellan Fund. Things have changed a lot in the meantime.

Lots of folks now pay to hear music on satellite radio, more than tripling shares of Sirius XM Holdings (ticker: SIRI) in the past three years. That's in addition to paying for online ad-free streaming music from the likes of Pandora Media ( P). Apple (AAPL) also paid dearly for headphone maker...